Language disorders resulting from focal brain damage can take a variety of forms, and there is evidence that some aphasic deficits are specific to the comprehension and interpretation of sentences. This project investigates the nature and causes of sentence processing disorders that occur in aphasia. The long-term goal is to develop a detailed model of sentence comprehension and production that can provide a functional explanation for the symptoms found in aphasia. Such a model would have a variety of applications. If specific aphasic symptoms can be interpreted as arising from identifiable processing deficits within a testable model, then attempts to remediate symptoms can be more defini- tively focused on the responsible representation or process. Moreover, discrete components of language processing that are identified through studies of aphasic patients would be likely to be the components that will, ultimately, prove to be localizable in the brain. The specific aims for the next project period test the hypothesis that two separable levels of structural representation are exploited during sentence processing. In separate tests of comprehension and production, the capacity to construct a constituent representation of sentence surface structures is distinguished from the ability to interpret the thematic roles of sentence nouns. The predicates to be used in these studies involve verbs and prepositions, with the goal of comparing the "mapping" between two levels of representation for each of these two predicate types. A series of "targeted intervention studies" is proposed in which specific deficits in the construction of each of these levels of representation is addressed in a treatment study, with the goal of measuring the effect of the intervention on hypothetically related, but untreated, components. In addition, development continues of a quantificational system for the analysis of sentence production deficits that expands the domain of application of the existing system to a wider range of aphasic deficits.